Travelers driving from Niamey, Niger, line up to be searched at the entrance of Gao, northern Mali, Tuesday. Soldiers from Niger and Mali patrolled downtown Gao on foot Tuesday, combing the sand footpaths through empty market stalls to prevent radical Islamic fighters from returning to this embattled city in northern Mali.

GAO, Mali — French soldiers on Wednesday recovered an enormous stash of explosives that authorities believe radical Islamic fighters were using to make bombs for attacks on northern Mali’s largest city, a Malian military spokesman said.

Daouda Diarra said that the French military removed some 800 kilograms (1,700 pounds) of explosive materials from a house in Gao’s Chateau neighborhood. The explosives had been discovered several days earlier, and the team had returned to the site Wednesday, Diarra said.

French military officials could not be immediately reached for comment.

Radical Islamic fighters withdrew from Gao on Jan. 26 after imposing their harsh interpretation of Shariah law in the most populous city in northern Mali for nearly 10 months.

Since their retreat, the Islamic extremists have launched two suicide bombings in the last week and invaded the city for a five-hour-long gun battle Sunday in the center of the city. Sunday’s brazen assault marked the first time the jihadists had penetrated the city of mud-walled buildings since they fled.

Last week soldiers combing abandoned jihadist hideouts also found a stash of NITRAM 5 explosives hidden inside rice bags that were left in a communal trash area. The explosives are manufactured for use in mining, but can cause considerable damage when used as bombs.

Two suicide bombers have detonated their explosives in attacks on military checkpoints since Friday. Neither of the attacks killed other people, but the pattern of attempts has raised alarm that the jihadists could be preparing to stage more devastating assaults on civilian centers.

One of the suicide bombers had stayed in a Gao house where Islamic extremists lived when they controlled the city. The guard there said it had been visited by the one-eyed Algerian terror leader Moktar Belmoktar, who was the architect of last month’s attack on a BP plant in Algeria in which at least 37 people were killed.

Soldiers from Niger and Mali have been patrolling downtown Gao on foot in an effort to secure the city. A new checkpoint with about two dozen Malian soldiers standing guard was also set up Wednesday near the waterfront.

Mali was plunged into turmoil after a coup in March 2012 created a security vacuum that allowed secular rebel Tuaregs, who have long felt marginalized by Mali’s government, to take half the north as a new homeland. In the following months, the rebels were kicked out by the Islamists who imposed strict Shariah law in the north, including amputations for theft.

France launched a military operation Jan. 11 against the Islamic extremists after they started to move south into government-controlled areas and captured key towns.